New NMEA 2000 install, many questions.

[Shavrfillet]

Looking for as much advice as possible. I will be installing a small NMEA 2000 system on my 1987 250 CCP. I currently have an older Yamaha 225 saltwater series (s225txrv) 1997. I know the engine will not be compatible with Nmea2000, but looking to repower in a year or 2. The components I will be installing are.
1. Garmin GPS741XS with Garmin GTM23M-TM transducer
2. Garmin GFS 10 fuel sensor
3. Garmin GMI 10 digital display
4. Garmin GPS19X  NMEA 2000 Antenna

Questions
1. which nmea 2000 starter kit to go with? Garmin, Lowrance or Maretron?
2. the transducer connects directly to the 741XS unit, will the GMI 10 see temp and depth through the NMEA 2000? or will i need to add a temp, depth and speed nmea 2000 transducer?
3. Can the backbone be cut to size with the field connectors installed? probably only need a few feet of backbone not 30.
4. I know I said above that my engine is not compatible with NMEA 2000, is their a company that converts older engine analog signals to NMEA2000 that i don't know about?

Appreciate any and all advice.
Thanks!!!

[wingtime]

Go with whatever brand N2K backbone and cables you want.  They are all compatible.  So I'd just find the best deal.  You basic N2K network will have two Ts.  One will be a standard Tee the other  power Tee (unless you have a device that supplies power to the network, but most do not). and two resistor ends.  Anything that you connect to the network will send data onto the network for other devices to see.  You may not need a GPS antenna to supply a GPS signal to the network if your 741 has a GPS in it.  The GMI 10 may see the temp from your transducer if the 741 sends that data out on the N2K network.  There are some analog to  N2K sensors out that that you could put on your existing engine.  I think Lowrance has a nice selection. 

Here is a good read on N2K:

http://continuouswave.com/whaler/reference/NMEA2000.html

[Aswaff400]

this will convert analog signals on old engines to N2K
http://www.nolandeng.com/catalog/product_info.php?cPath=24&products_id=37

what is the reason for wanting the GMI display?

 the built in gps antenna in the garmin should be strong enough to read even if flush mounted so the n2k antenna may not even be needed. my 840xs has no problem reading the sky and its flush mounted. dont cut any wires to make them shorter! i have my power coming from ignition on so the only time the n2k devices will work is if the key is on. all garmin devices will talk to each other and display garmin info on the network. you can even connect other brands to the n2k network to display engine gauges on multiple displays but will not share gps or sonar info. i plan on adding a second display on my boat and havint the N2k network makes it simpler.

[Shavrfillet]

Aswaff400, thanks for the info.
The reason for the GMI10 is so that I can have full screen Nav on the 741xs and have water depth, fuel flow, fuel quantity and other functions on the GMI10 at the same time. Will be navigating in plenty of shallow water.  I've read everything about the 741xs and haven't found anything about it sharing GPS, water depth, GPS coordinates, water temp etc with the N2K system.? That's the reason for the exterior antenna as well.I hope I'm wrong. I plan on wiring it up to the ignition switch as you did.
Thanks again!!